Association between low maternal Body Mass Index (BMI) and the co-occurrence of multiple forms of childhood undernutrition: a systematic review and meta-analysis

Low maternal Body Mass Index (BMI) is a critical risk factor for child undernutrition. While its association with single anthropometric deficits such as stunting or wasting is well documented, evidence on its relationship with the co-occurrence of multiple forms of undernutrition remains scarce. The Composite Index of Anthropometric Failure (CIAF) is a summary measure that classifies children as having anthropometric failure if they are stunted, wasted, underweight, or any combination of these, thereby capturing both single and concurrent deficits. This systematic review and meta-analysis explored the relationship between maternal underweight and CIAF in children under five, addressing a significant research gap. We systematically searched major databases, including MEDLINE (PubMed), Embase, Scopus, CINAHL, ProQuest (EBSCO), ScienceDirect, Global Index Medicus, and the Cochrane Library, without language or geographic restrictions, to identify relevant observational studies. We pooled extracted confounder-adjusted odds ratios (ORs) and 95% confidence intervals (CIs) using an inverse-variance weighted random-effects meta-analysis, with heterogeneity assessed using the I² statistic. Sensitivity analyses were conducted to evaluate the robustness of the results, and subgroup and meta-regression analyses were performed to explore heterogeneity. Pooled prevalence ratios (PRs) and prevalence differences (PDs) were estimated to quantify the relative and absolute inequalities in CIAF prevalence between children of mothers with normal weight and those with underweight mothers, respectively. A total of 19 studies, comprising 536,840 mother-child pairs, were included in the final analysis. Children of underweight mothers, compared with those of normal-weight mothers, had 34% higher odds of CIAF (pooled OR: 1.34, 95% CI: 1.25–1.44, n = 375,248), with significant relative (pooled PR: 1.32, 95% CI: 1.06–1.64) and absolute inequalities (pooled PD: 0.13, 95% CI: 0.03–0.23). Subgroup analysis by geographic region showed a significant association between low maternal BMI and increased CIAF odds in children under five (pooled OR: 1.47, 95% CI: 1.39–1.56 in Asia; pooled OR: 1.16, 95% CI: 1.12–1.20 in Africa). No significant evidence of publication bias was detected. These findings indicate that low maternal BMI is significantly associated with an increased risk of CIAF in children under five. Substantial inequities in CIAF prevalence exist across maternal BMI groups, with children of underweight mothers disproportionately affected by higher burdens of CIAF. Prioritising nutritional interventions that address maternal underweight during preconception and pregnancy is essential to reduce multiple forms of undernutrition in children.